Request Read Receipt Checked yes by Default?

[Eq4bits]

vB4.2.3
I would like the 'track pm' radio button checked by default for my members that meet the conditions for $show['tracpm'].

I tried changing the 'value="1"' to a 'value="0"' in the following bit of the pm_newpm template

PHP Code:

<vb:if condition="$show['trackpm']">
                    <li>
                        <label for="cb_receipt"><input type="checkbox" name="receipt" value="1" id="cb_receipt" tabindex="1" {vb:raw checked.receipt} /> {vb:rawphrase request_receipt_for_message}</label><p class="description">{vb:rawphrase request_receipt_for_message_desc}</p>
                    </li>
                    </vb:if> 


Saved
Cleared Forum/System Cache
But it didn't make any difference. I also looked for it as a setting in options>settings but couldn't find it.
Help?